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首页> 外文期刊>Chemistry: A European journal >A One-Pot Synthesis of(E)-Disubstituted Alkenes by a Bimetallic [Rh-Pd]-Catalyzed Hydrosilylation/Hiyama Cross-Coupling Sequence
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A One-Pot Synthesis of(E)-Disubstituted Alkenes by a Bimetallic [Rh-Pd]-Catalyzed Hydrosilylation/Hiyama Cross-Coupling Sequence

机译：双金属[Rh-Pd]催化氢化硅烷化/ Hiyama交叉偶联序列一锅法合成（E）-双取代的烯烃

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摘要

A bimetallic [Rh-Pd] catalyst was prepared by soaking into an iodide ionic gel an equimolar solution of [RhCl(PPh3)3] and Pd(OAc)2 in CH2Cl2.Its catalytic activity was evaluated by rhodium-catalyzed hydrosilyla-tion(H),palladium-catalyzed Hiyama coupling(C),and in the one-pot hydro-silylation/Hiyama coupling sequence(H/C).It was found that the homogeneous combination [RhCl(PPh3)3]/NaI was a superior system compared to the polyionic mono-and bimetallic rhodium catalysts in the hydrosilylation of terminal alkynes.Interestingly,the most effective catalyst in terms of stereo-and chemoselectivities was ob- served to be the bimetallic ionic gel [Rh-Pd] in the one-pot process leading to(E)-alkenes with good yields.The remarkable stereocontrol is ascribed to a beneficial Pd-catalyzed isomerization from the mixture of stereoisomeric vi-nylsilanes obtained in the initial hydrosilylation step into the more stable(E)-adduct.The [Rh-Pd] heterogeneous catalyst also showed a higher chemose-lectivity than the homogeneous catalyt- ic combination,and no detrimental formation of Sonogashira side product was observed due to an ionic-gel-mediated kinetic modulation.To illustrate its scope and limitations,the described one-pot bimetallic catalytic sequence was extended to functionalized terminal alkynes and various iodide substrates.Conjugated systems,such as hy-droxycinnamaldehyde,dienes,and tri-enes,were synthesized in good overall yields.To avoid deactivation of the Rh species,N-heterocyclic iodides had to be added sequentially after completion of hydrosilylation.
机译：将[RhCl（PPh3）3]和Pd（OAc）2等摩尔溶液浸入碘离子凝胶中，制得双金属[Rh-Pd]催化剂，并通过铑催化的氢化硅烷化反应评价其催化活性。 H），钯催化的Hiyama偶联（C）以及一锅加氢甲硅烷基化/ Hiyama偶联顺序（H / C）。发现[RhCl（PPh3）3] / NaI的均质组合优于在末端炔烃的氢化硅烷化反应中，与多离子单金属和双金属铑催化剂相比，有趣的是，就立体和化学选择性而言，最有效的催化剂是双金属离子凝胶[Rh-Pd]。锅法制得（E）-烯烃的收率很高。出色的立体控制归因于钯的催化异构化，该异构化是从最初的氢化硅烷化步骤中获得的立体异构体乙烯基硅烷混合物转变为更稳定的（E）加合物。 [Rh-Pd]多相催化剂也显示出更高的化学选择性与均相催化组合相比，由于离子-凝胶介导的动力学调节，未观察到Sonogashira副产物的有害形成。为说明其范围和局限性，将所述一锅双金属催化序列扩展至功能化的末端炔烃以高收率合成了共轭体系，例如羟基肉桂醛，二烯和三烯等。为避免Rh物种失活，必须在氢化硅烷化完成后顺序添加N-杂环碘化物。

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